That's right, but I would go one step further and have F(irst) and R(est), with obvious composition as follows: (using kruhft's examples from another thread)

    (ff  x) == (caar  x) == (car (car x))
    (rrf x) == (cddar x) == (cdr (cdr (car x)))

I would argue that it's worth sacrificing the 'f' and 'r' symbols for such a common construct.

If not, a common prefix (lacking in HD and TL) could be used:

    (.ff  x) == (caar  x) == (car (car x))
    (.rrf x) == (cddar x) == (cdr (cdr (car x)))

Yes, I realize I'm 55 years late to the party.